1. Field of the Invention
This invention relates to a hydrophone mounted on the hull of a ship, and associated equipment on board ship, for detecting, measuring, recording, and listening to sound signals received from distant sound sources under water. More specifically, the invention relates to ceramic hydrophone transducers with associated electrical and electronic components which generate a voltage signal in response to underwater acoustic sound signals received from distant sources in which the noise generated on board ship and transmitted to the hydrophone via the ship's hull and the hydrophone mounting structure is suppressed.
2. Description of Prior Art
Hydrophones and related equipment for underwater detection of sound, such as the sound generated by submarines, as well as the suppression of such sound, have been the subject of much research effort. Noise transmitted by the hull of a ship to a transducer has been minimized by placing the transducer in an evacuated casing (U.S. Pat. 3,115,616). Laminated acoustic panels have been proposed for absorbing sound in water and elsewhere (U.S. Pat. Nos. 3,215,225, 3,923,118, 3,647,022, and U.S. Pat. No. 3,614,992). The frequency response of a hydrophone transducer has been improved by negative feedback to the transducer via a feedback electrode (U.S. Pat. No. 4,709,360). Noise transmission from a ship's hull to a hydrophone mounted on the hull has been minimized by using flexible supports and attaching heavy masses to the hydrophone so as to dampen out noise from the ship transmitted to the hydrophone via its support.